High performance parts 10hp Tejuckseh.

Hi to All, Title is just a joke. Briggs and Scrap em is just as bad in today's market! Man I mess the old school small engines. Nothing has the sound of a H50 Tecumseh. They sound awesome on a mini bike, half wore out with a bit of Piston Slap! I personally prefer the engine with roller bearings on the crank journal. Anyways to my question at hand!!!!!!!! Does anyone know any tricks to hop up a 10 horse Tecumseh horizontal shaft. She is a older one. How could I get ahold of a higher lift cam. And what could I do to juice the old girl up. Just for fun!! Thanks to you all!! Injoy


Unfortunately, when it comes to HM80, 90, and 100 engines most of what you can do with them is finding Tecumseh Star engine parts, finding parts from other engine manufacturers that will work, or spending a lot of money for custom work. ARC racing does make a billet connecting rod that costs ~$140 made for the HM100. Valve springs can be sourced from VKE motor sports sometimes. Can help getting parts in general as they build jr drag engines based off the Tecumseh Star engine.

The Tecumseh Star engine is a racing HM100 Tecumseh used to make. The model most people look for parts off of is the SBH9992 as it had a hot cam, heavier valve springs, and a billet connecting rod. That said about the Star engine, I understand it still didn't much like cracking 6k RPM since the cam apparently wasn't hardened and the valves started to float getting over 6k. I may be entirely wrong about that though, it's just what I've read online a number of places and those things have a habit of being apocryphal if they aren't direct from the manufacturer specs.

Edit: As an added bit. Here is the parts diagram and listing with part numbers from jacks small engines. The parts that have are ######k are specific to the star engine. You will also note, none of them are available to order.

Last edited:
That seems pretty heavy for a mini bike.
Arguably, it is. It's also a blast when you punch the gas and it threatens to rocket out from under you while attempting to rattle every weld on the bike loose. Lock washers and nylock nuts on every bolted connection are a requirement. To date my HM80 has rattled the exhaust off, rattled the intake loose, rattled the headlight and tail lights off their mounts and loosened the bolting at the handlebars before I started lock washering and nylocking everything. That reminds me, the exhaust strap came loose again, I should tighten that up tomorrow...

I should weigh my bike sometime. It probably cracks in close to 125 lb when everything is bolted on.
I’m with massacre way too heavy….for a fun ride….I think if you’d just build a hs50 with all the bells and whistles you’d be shocked at with they will do…

you can gear them up too


Well-Known Member
i'm with both skipp and mass on this too. i've put the hm10 motor on a Harrison and a super bronc with an open exhaust, slide carb, series30 TC. the damn bikes were a monster to ride, loud as hell, and it wanted to kill me. it's just not fun. i put a modified HS50 on the harrison (sold the bronc), and that made all the difference, it became fun again. that said, i have an Hm80 eight horsey i was considering trying on a 14" wheel speedway. but just have not done it yet...